A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.
Chuzhou, for short, is called Tuzhong, Qingliu and Xinchang in ancient times. It is the municipality of Anhui province, the city of Nanjing metropolitan area, the core city of Hefei metropolitan area, the member city of Yangtze River Delta urban agglomeration, the Jiangbei gate of Nanjing, the northern wing city of national Wanjiang demonstration zone, the central city of eastern Anhui, and the important hub city of Jianghuai region. Chuzhou is located on the north bank of the lower reaches of the Yangtze River, the western end of the Yangtze River Delta, the eastern part of Anhui Province, and the confluence area of Jiangsu and Anhui. The city has 2 districts, 4 counties under jurisdiction and 2 county-level cities in escrow, with a total land area of 13398 square kilometers and a resident population of 4.03 million. Chuzhou was the land of Tangyi as early as the pre-Qin period (now Nanjing.